The present invention relates generally to elevator group controls and, in particular, to a method and apparatus for modernizing the control of an existing group elevator control.
During the modernization of an older group elevator control, wherein the older elevator controls are replaced with new controls, a method of providing optimum elevator service to the building is required. Unless other provisions are made, the serving of hall calls is restricted to either the elevator cars of the group still connected to the original group control or the elevator cars of the group connected to the updated group control which reduces the conveying capacity of the elevator group and thereby leads to prolonged waiting times. Various methods of handling this problem are known from the prior art. In a first method, new and old push button hall call fixtures are located at each floor during the changeover period. This method, however, allows the passenger to select his preference and therefore may cause traffic loading imbalance. Also, some passengers might select a push button on each fixture requiring elevator cars from each system to answer a single hall call. Furthermore, the presence of two push button fixtures on each floor may lead to passenger confusion.
In a second method, preferably applicable to older systems, during the changeover period, the elevator cars connected to the original and the updated group controls are adjusted to serve separate floors, so that two elevator cars would not be assigned to answer identical hall calls. One basic drawback to this method is that when one control has a malfunction, floors assigned to that control are not served. Moreover, the push button fixture wiring has to be relocated depending on which group control each floor has been assigned to. In addition, heavy demand floors like lobby or restaurant floors are served inefficiently.
In another method, during the changeover period, the original group control and the updated group control are interconnected to allow all elevator cars to see the same hall call. Unless the voltage supplies for the original and the updated controls are similar, which seldom is the case, the relay dispatch panels have to be hard wire interconnected and voltage interface relays are necessary. It also is disadvantageous in that a hall call is seen by both controls and, therefore, a car from each group is assigned to serve each hall call. The car which arrives first causes the call to be cancelled, while the second car has to make a false stop. This method cannot be used when the updated elevators are under distributed control, i.e., in microprocessor-based systems.
Finally, an overlay method has been used wherein, during the changeover period, the elevators connected to the original group control are overlaid with the same control strategy as the updated group control. One major drawback to this method is that the old control must be changed to enable it to be accessed by the newer system circuitry which may present problems since the designers of the newer system control may not understand the original design strategy. As overlaying an existing control provides an opportunity for causing extensive damage, this method requires the design engineer and the installation technician to have a detailed understanding of the existing control method. It is a further disadvantage of the overlay method that it necessitates extensive modification of existing controls. Such modification may require several days of field labor per car, whereas the overlay equipment is probably discarded upon completion of the modernization. Thus, the overlay method is expensive.
A more recent innovation is described in the German Patent No. DE 35 09 223 which shows a method and equipment in which adaptation computers make the existing old elevator group control compatible with the new group control to be installed. However, an adaptation computer is required for each elevator car of the elevator group to be modernized. The adaptation computers and the new group control are connected with each other in the elevator group to be modernized such that the adaptation computers follow the operation of the old elevator control, but cannot control this operation. The changeover of the individual elevator cars takes place in a three step process. An elevator car to be re-equipped is first taken out of service, then subordinated to the new group control in that the output lines of the corresponding adaptation computer are connected with the control lines of the associated elevator control unit, and finally placed into operation under the control of the new group control. This three step process is repeated for each elevator car until all cars are connected to the new group control and the modernization of the elevator group is concluded.
Since the last described method requires a permanently installed adaptation computer for each elevator car of the elevator group to be modernized, the basic disadvantage is that the method and the apparatus are relatively expensive. This applies particularly when the control device of the elevator itself, for example the control of the old drive or the equipment in the shaft, is also modernized at the same time as the group control. In this case, it would be advantageous to use control elements which are compatible with one another so that permanently installed expensive adaptation computers and their programming could be eliminated. A further disadvantage results from the special knowledge that is required for the configuration of the adaptation computers and that the operation of both old and the new control elements must be known in detail. This method also includes a substantial change in the existing control system which is a risk for the operating and safety functions.